Ruy Lopez with a4

I have noticed some games in the closed variations of Ruy Lopez where white plays a4. It seems to be quite a common theme in many lines. I have seen it in the Archangel and the chigorin amongst others. Clearly it has some immediate tactical threats in that it threatens to win a pawn, but GM's don't make moves like this just to threaten an easily defended pawn (black just has to defend his a8 rook). There must be more sound positional reasons behind it, but I don't really see it. It just looks ugly and weakening to me.

Here is an example in case you are wondering what I'm talking about.

Any Ruy Lopez experts want to help me out? I decided to take this opening up recently and I have never had to learn so much about chess before. So much going on here!

Does anyone really play 9 a4 against you? It's a rare move in practice - White more often tries 9 h3 to avoid the pin, 9 d4 disdaining the pin, or 9 d3 heading for less critical variations.

a4 is a useful move for White in many lines, but not this soon - except in the case of 7...0-0 8 a4 where it is designed to avoid the Marshall Gambit.

Ahhh you misunderstand, I am trying to learn to play the opening as white. So I have studied a bunch of games and over and over again I see this move a4 at some point, often quite early in the opening and I am left wondering why it was played. I wondered if it was some common positional theme rather than a tactical ploy that is going over my head.

a4 is a standard way of avoiding the Marshall Gambit: a wise choice, since I don't know how to ride out the storm in that variation.

If played at the right time, a4 can destabilize Black's position, just when he thinks the game is quieting down. Timed wrong, it just opens a file for Black to contend for and lets Black off the hook from the traditional King-side attack.

Timing is everything. In the diagram above, it does look poorly timed.

Yes I understand I think. You are right, when I saw the a4 early it was not in this position and on checking you are right it is the anti marshall thing. In the Archangel their is an early a4 with some crazy tactics associated with it. And later, yes I see. The threat of opening up lines on the q side ties down blacks pieces so even though white mostly never utilises that threat (which is why I could never see any concrete reason for doing it) it still has an effect and in a way aids whites kingside attack! Is that right?

The Ruy Lopez is a lot like the cold war! It is more a case of threats and manouvers rather than outright battles and skirmishes.

Im starting to think that if you want to improve your chess game you should study every aspect of the Ruy Lopez and by the time you understand every subtlety in it you will be very very good indeed!

Yes, it's the logic of the Lopez that impresses me with it. You are just about impelled forward to positions that, while cluttered looking, make perfect sense. To avoid this march of fate, some try to jiggle some initiative out of it by destabilizing the game early on with things like 3...Nd4 (Bird Var) or the Archangel or Schlieman.

This allows White to continue with his slow but sure buildup on the kingside with moves like Nb1-d2-f1-g3(or e3). If White doesn't play a4 Black's pieces and pawns swarm all over the queenside and White's a1-rook suffocates.